Diesel exhaust fluid (DEF) is used in selective catalytic reduction (SCR) technology to reduce nitrogen oxide emissions in diesel engines. As manufacturers move to reduce these emissions across their product lines, SCR technology is moving beyond over-the-road trucks into various construction machines, such as graders, pavers, compactors, dozers, and others. DEF is consumed as the diesel engine operates, generally at a rate of 2-3% of fuel use and requires that DEF be stored on the machine so that the SCR technology can operate continuously as the machine is run.
However, DEF is sensitive to high temperatures that can significantly shorten the storage life of the DEF. Construction machines using DEF often operate in hot conditions. In a compactor, for example, hot asphalt from the paving surface adds to heat in the engine compartment generated by the engine so that ideally, a DEF storage tank would be located away from the engine compartment in order to prolong the DEF shelf life. In addition, locating a DEF storage tank inside the engine compartment can require removing bulky engine covers when refilling the tank. However, in many construction machines there are no suitable locations for DEF tanks outside the engine compartment, due to other moving parts, potential exposure to physical damage, operator station access or sightlines, etc.
U.S. Pat. No. 9,036,018 (the '018 patent) discloses a DEF tank inside an insulated box. However, the '018 patent achieves heating and cooling of the DEF exclusively using a secondary line that is routed into the DEF tank. Fluid in the line heats or cools the fluid as needed.